Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may be composed of both gaseous and solid material, such as, for example, particulate matter. Particulate matter may include ash and unburned carbon particles called soot.
Due to increased environmental concerns, exhaust emission standards have become more stringent. The amount of particulate matter and gaseous pollutants emitted from an engine may be regulated depending on the type, size, and/or class of engine. In order to meet these emissions standards, engine manufacturers have pursued improvements in several different engine technologies, such as fuel injection, engine management, and air induction, to name a few.
In addition, engine manufacturers have developed devices for treatment of engine exhaust after it leaves the engine. For example, engine manufacturers have employed exhaust treatment devices called particulate traps to remove the particulate matter from the exhaust flow of an engine. A particulate trap may include a filter designed to trap particulate matter. The use of the particulate trap for extended periods of time, however, may enable particulate matter to accumulate on the filter, thereby causing damage to the filter and/or a decline in engine performance.
One method of restoring the performance of a particulate trap may include regeneration. Regeneration of a particulate trap filter system may be accomplished by thermal regeneration, which may include increasing the temperature of the filter and the trapped particulate matter above the combustion temperature of the particulate matter, thereby burning away the collected particulate matter and regenerating the filter system. This increase in temperature may be effectuated by various means. For example, some systems employ a heating element (e.g., an electric heating element) to directly heat one or more portions of the particulate trap (e.g., the filter material or the external housing). Other systems have been configured to heat the exhaust gases upstream from the particulate trap, allowing the flow of the heated gases through the particulate trap to transfer heat to the particulate trap. For example, some systems may heat the exhaust gases upstream from the particulate trap, with the use of a burner that creates a flame within the exhaust conduit leading to the particulate trap. Other systems may alter one or more engine operating parameters, such as air/fuel mixture, to produce exhaust gases with an elevated temperature. Running an engine with a “richer” air/fuel mixture can elevate exhaust gas temperature. Some systems may increase a parasitic load on the engine, while maintaining a constant engine speed. In order to do so, additional fuel may be injected, resulting in a richer air/fuel ratio and raising the exhaust gas temperatures.
Regeneration may be performed periodically as opposed to constantly. That is, after a trigger condition occurs, the thermal regeneration system may initiate regeneration in response to the trigger condition. Some systems are configured to elevate exhaust gas temperatures by increasing parasitic load on the engine. For example, one such regeneration system is disclosed by U.S. Patent Application Publication No. 2004/0172935 by Otake et al., published on Sep. 9, 2004 (“Otake et al.”). Otake et al. disclose increasing the load of auxiliary devices, such as an air-conditioner compressor.
While the Otake et al. system may be configured to elevate exhaust gas temperatures by increasing parasitic load on the engine, the Otake et al. system achieves such an increase in load by also increasing engine speed.
Further, the Otake et al. system requires the presence of auxiliary devices to elevate exhaust gas temperatures. Engines may provide power for many different kinds of equipment, including stationary equipment or other kinds of unmanned equipment, such as electric power generation sets. Unmanned equipment would not be equipped with an air conditioner. Therefore, the Otake et al. system could not be implemented on such equipment.
The present disclosure is directed to solving one or more of the problems discussed above.